Paper product and method of making the same



Patented May 5, 1931 UNITED STATES- PATENT orr cr.

HAROLD ROBERT RAPTON, OF LAWRENCE, MASSACHUSETTS, ,ASSIGNOR TO RALFI'OLD PROCESS CORPORATION, A CORPORATION OF MASSACHUSETTS PAPER PRODUCT AND METHOD OF MAKING THE SAME No Drawing.

This invention relates to the manufacture of paper and more particularly to an improved sized paper containing a carbonate filler and to a method of making the same.

The principal object of this invention is to provide a sized paper made with a carbonate filler in such manner that the sizing effect of the sizing agent or agents employed which has been wholly or in part deteriorated 30 due to the effect of the carbonate filler is substantially completely restored.

An important object of this invention is to provide asimple and efficient process of makmg an improved sized paper wherein rosin size and alum are employed in the beater for sizing the paper mix and wherein a carbonate filler is added to the mix in the beater, and wherein an additional amount of alum is added to the paper mix at a later point in the process.

Another object of this invention is to provide a process of making sized paper wherein p a sizing restoring agent is added to a previously sized paper mix containing a carbonate filler at such a point in the process that the time and intimacy ofcontact between the sizing restoring agent and the constituents of the mix is materially'limited.

A further object of this invention is topro- 1:0 vide a process of making sized paper which differs from present paper making procedure wherein rosin size, alum, and a filler are added to fibrous material in the beater only in the addition of a subsequent quantity of alum to the previously prepared mix at a point to be later indicated subsequent to the primary beating step but prior to the passing of the mix onto a web-forming device of a paper machine.

Other objects and advantages of this invention will become apparent during the course of the following description.

As will be apparent to those skilled in the art, it is customary to employ substantially the following procedure in modern paper Application filed September 5,. 1928. Serial No. 304,168.

making practice: Fibrous materials together with filler, size, such as rosin size, size precipitant, such as alum, and coloring matter if desired, are ordinarily mixed in a beater or the like at a dry solid content of approximately 5 per cent. or slightly higheryand are subjected to a heating'treatment in the beater, the amount of such treatment depending upon the type of paper which is to be made. The paper mix is then ordinaril discharged from the heater and introduced into a container commonly called a beater chest, additional Water usually being added. Thereafter the mix is pumped from the beater chest to a suitable refining engine, usually a jordan, at a dry solid content of approximately 4 per cent. In common practice the mix is usually diluted somewhat by. the addition of water, and the diluted mix is ordinarily conducted from the jordan to another container commonly known as a machine chest. From the machine chest the mix is pumped to a point near the web-forming end of the paper machine where it is largely diluted with water, water being added ordinarily in such an amount as to provide a dry content of'from approximately to 1 per cent. or slightlyhigher,but practically never in excess of 1 and per cent. Themlx in such highly dilute condition is then passed through rifflers or the like if desired and thereafter through screens and through the head box of the paper machine onto the machine wire or into the vat depending upon Whether a. Fourdrinier or a cylinder machine is employed, and during this passage additional amounts of water are usually added in the form of sprays or otherwise. This exact procedure is not always followed but in some instances is modified in accordance with the type of paper being made. For example, in the manufacture of certain types of paper, the beating process is almost or entirely dispensed with, the ingredients of the stock be ing merely mixed prior to jordaning. In.

some instances the step of refining or jordaning may be partially or wholly dispensed with. Moreover, the arrangement of the chests in respect to the mechanical treating apparatus is not in all cases precisely as described above.

The time consumed from the point of mixing the ingredients in relatively concentrated state up to the point where the stock is to bediluted for delivery to the web-formin g exists in a dilute stage prior to its delivery to the web-forming end of the machine is in some cases a matter of only a few seconds and ordinarilycnot over a minute. Even under extreme conditions the time would never be in excess of 5 minutes.

In many instances the water supplied to the beater and also the water employed for dilution at the jordan as well as for the final dilution of the mix before delivering to the webforming end of the paper machine consists in whole oriiin part of white water by which term is meant to be in chided all efiluents from the web-forming end of the paper machine. It will be apparent therefore that this water functions cyclically in the process and that there may be reintroduced into the earlier stages of the process part of the material which was derived from the web-forming stage of the process, such material being returned through the medium of the white water.

Moreover in modern paper making practice there is a tendency to reclaim the ingredients contained in the white water, sometimes merely from that portion of it which is in excess of that which can be or is to be used cyclically in the process, or sometimes from a portion or from all of that which is to be used cyclically, or both, by subjecting the white water to some suitable procedure, as filtration, such for instance as deckering' or actual passage through a filtering machine, or sedimentation or the like, thereby passing out the substantially purified aqueous eflluent to waste, or for further use in the pulp or paper making process, with the simultaneous return of the recovered material to the paper making process. In some installations this recovered material may be returned to the beater, while in others it may be returned to the beater chest, machine chest, or other point in the process if desired.

It will therefore be apparent that independent of the exact type of apparatus and procedure employed, the following operations are normally employed in the paper making process; the mixing of the ingredients in relatively concentrated form; their contact in such concentrated form for a relatively long period of time; their subsequent dilution to a concentration suitable for delivery to the web'forming end of the paper machine; their remaining in such dilute condition a relatively short period of time; and the recontacting of the mixture of the ingredient-s prior to its delivery to the webforming end of the paper machine with the cyclically returned white water and/or material recovered therefrom. Under these conditions, where carbonate fillers have been employed in the paper making process, it has been found in some'cases-that the sizing effect has been appreciably affected, or more commonly; that the sizing effect has been completely destroyed.

Although the practical sizing results of the use of alum and rosin size in ordinary paper making practice have been known for a long period of time, nevertheless there is as yet no unanimity of opinion as to the exact chemistry of the sizing process. Some workers in this field assert that the sizing is due purely to the adsorption of the rosin from the sizing material by the cellulose fibre and the fixing of it thereon by the oppositely charged aluminum compound. Others maintain that a precipitate of aluminum resinate is responsible for the sizing, and still others hold that the free resin in the size is the major or entire sizing factor. Inasmuch as there is no generally accepted view as to the chemistry of sizing, it is difficult to explain chemically the exact'effect of carbonate fillers on rosin sizing. However, whatever may be the reason which theory may assign for this effect, the actual results obtained in some cases where carbonate fillers have been employed are as described in the preceding paragraph.

As a result of careful experiment, I have discovered that a mix made from fibrous ma- .terial, size, such as rosin size, a size precipi-.,;

of the paper machine. Thus the material 1 constituting the sizing, the effect of which has been deteriorated or destroyed, acts as a potential sizing agent which is made efi'ectual through the addition of a restoring agent. Thus where I use the expression powhereas the restoring agent subsequently added acts to restore the efficacy of the previously precipitated sizing, the (effect of which has already been deteriorated or destroyed.

I have also discovered that this restoring action is relatively sensitive and of relatively. brief duration and if the attempt is made to effect the restoration in the mix when'it is relatively concentrated, and particularly when the relatively concentrated mix-is subjected'to agitation as is normal in the stock chests in paper making, that the restorative action is again destroyed. I have further discovered that if after applying the restorative action the mix is subjected to a minimum degree of intimate contact and a minimum of time of contact, such as is the case when the mix is in dilute form prior to its delivery to the web-forming end of the paper machine, then the restorative action is practically not affected or only slightly affected according as theintimacy and/or time of contact may be lesser or greater. Also I have found that agitation in the dilute state has a very much less injurious effect than in the concentrated.

Based on these discoveries, I have devised a method whereby they may be applied practically to paper mill operation and sized carbonate filled papers be reliably produced thereby. I have found in general that acidic material and/or salts of trivalent metals, as ferric iron or aluminum, act as restorative agents. For instance, I have found that it is possible to restore the sizing effect to a mixcontaining carbonate filler in which the sizing'effect has been destroyed, by addition of an acid such assulphuric acid (H SO I have also found that it is possible to use acid salts such as sodium bisulphate (NaHSO However, the best agents I have so far found are the salts of the trivalent metals, as ferric iron or aluminum, and of these aluminum has bymy tests to date proven to be the better. Ferric iron may be" used in papers other than white, but for white papers, aluminum is the most suitable material, and evenforcolored papers, its relatively greater effectiveness may render it more economical.

Of the aluminum salts available the chloride, sulphate, or the like, or the-double salts which are the true alums, maybe used, but because of economy, the ordinary sulphate of aluminum normally known as alum is most suitable. I have found that anyof the ordinary types of alum are satisfactory, whether acid, neutral, or basic.) I have also found that whereas the acidic materials mentioned in ,the precedingaparagraph can be used and although some'of "them are considerably cheaper than alum, the effectiveness of alum seems to be sufliciently greaterin proportion to the above mentioned materials, that it becomes economical to use alum instead of these relatively cheaper materials.

Because of the uncertainty as to the chemistry of the sizing reaction as indicated above, it is not quite clear just why this restoring .action of the acidic or aluminous materials takes place If this deteriorating effect be due to the. gradual transformation of the alum-rosin compound into an alkaline earth metal resinate, then the addition of the restorative material may cause a reversal of this reaction. However, it is to be clearly understood that whatever be-the theory underlying the restorative action, my invention is not limited or controlled-by an theory, and is entirelyindependent thereo because the facts ofthe case are, regardless of theory, that such materials do cause a restorative action to the sizing in carbonate filled papers, thereby producing sized carbonate filled papers, which without these restorative agents would have their sizing damaged, if not completely destroyed.

The preferred method which I employ consists substantially in adding, a subsequent portion of alum, preferably continuously, in-

In the preferred practice of myinvention I I add to the beater or other similar or mixing on compounding or disintegrating or treat ing machine, all the fibrous materials, excepting those falling within the definition of carbonate fillerhereinafter set forth, such as broke or the like, and such fibrous material as is in the stock recovered from the white water in the paper making process, and then add rosin size and alum. After the rosin size.- alum compound has been formed on the fibre, I may then add the fibrous materials coming under the definition of carbonate filler hereinafter set forth and the carbonate filler itself. It is'possible to add all'the fibrous constituents and/or the carbonate filler itself in the beater prior to the addition of the alum to the size in the beater, but my experiments I have indicated that better results are obtainable when the rosin size-alum compound is formed onthe fibre in the absence of any carv bonate filler.

Moreover, in furnishing the beater I prefer to employ fresh water or white water which has been clarified so that the alum-rosin precipitate may be completely formed on the fibre before the addition of carbonate filler in any form to the mix..

In regard to the mixing of ingredients of fibre (free from carbonate filler), alum and rosin size in the beater, I do not restrict myself to any given order of the addition of these ingredients as I may use any order of mixing as is suitable in paper making practice. liurthermore may add the ingredients in one or more parts or steps at any point prior to the addition of the carbonate tiller. For example, as is sometimes customary in the paper making practice in the case of hard water, I may add part of the alum first to the fibre and water to render harmless to the rosin size the injurious ingredients in the hard water and then I may add the rosin size followed subsequently by the remainder of the alunn Furthermore tillers of types other than carbonate tillers may be also added in the beater if it be desired to employ them in conjunction with the carbonate fillers in the paper, as well as coloring materials, and other substances which may normally be added in the paper making process. Moreover, if it is desired, starch may be added to the mix in the beater or other point in the process, attention being directed to my copcnding application Serial No. 202,453 of June 29th, 1927. The mixin the beater is then given the usual treatment, passed through the beater chest, jordan and machine chest. All waters used subsequent to the-precipitation of the rosinalum compound in the beater may be either fresh water or white Water, as desired.

The mix still in relatively concentrated form is now at the point where it is ready for dilution preparatory to delivery to the webforming end of the paper machine. Here the white water from the paper machine may be used as diluting water. At this point or subsequent thereto, alum is added preferably continuously, preferably in solution, the precaution being taken that adequate mixing of the alum, the white water and other water if used, and the relatively concentrated mix coming from the machine chest be assured. A separate mixing box may be provided if desired but under ordinary machine practice this is unnecessary as there is usually adequate provision made in paper manufacturing to insure thorough mixing of the relatively concentrated mix with the diluting water. I have found in practice that it is also satisfactory to add alum at a subsequent point in the process, for example, just prior to the passage of the diluted mix to the screens, the screens effecting Very thorough mixing in this case. If, however, the alum is actually added at the head box of the machine subsequent to the screens, then care should be taken that adequate distribution and mixing of the ingredients is insured by proper bafiling or the like.

An illustrative furnish which may advan- Restoring agent, e. g. alum (Al (SO .18I-I 0) tageously be used in practicing my invention is as follows:

Carbonate filler, e. g. calcium carbonate magnesium hydroxide 300 M atcrz'al added to misc proportionately and continuously on dilution Pounds Another illustrative furnish is as follows:

Materials added in the beater M atem'al to be acldecl pro ortionatcly and continuously on z'lutz'on Pounds Restoring agent, e. g. alum (AI:(SO,) -,.18H:O) 75 In the above formulw, the weights of size and carbonate filler refer to the bone dry basis, the weights of all other ingredients being given on the air dry basis.

In either of the above furnishes starch may be used as set forth above. It may be conveniently added to the beater subsequent to the addition of the carbonate filler, or otherwise if desired. Suitable coloring matter may be added if desired.

The illustrative furnishes given above produce a satisfactorily sized paper, and as will be apparent the sizing can be increased or decreased by varyin the amounts of sizing ingredients used. T do not restrict myself to any given quantities of size and alum in the boaters, nor to any given quantity of alum to be used after dilution, as I have found that these quantities may be very widely varied and still give satisfactory results.

The resultant papers made by my process may be used for such purposes as those to which sized filled papers are normally put including that as a raw stock for further conversion, as for example, for coating.

As is set forth above, the primary object of my invention is to restore the sizing in the paper mix containing carbonate filler by the addition of a restoring agent such as alum. Under conditions ordinarily obtaining in paper mixes, this restoring agent would react chemically with the carbonate filler and thus be destroyed. However, I am able to obtain the desired effect of this restoring agent in the paper mix and thus obtain sizing by adjusting conditions under which the restoring agent is added so as to substantially prevent it from reacting chemically with the carbonate filler. There is therefore substantially no conversion of the carbonate filler into a neutral compound by reaction with the restoring agent,

andthe carbonate filler continues to exist in themix. Whereas I have not limited myself to an definite amount of carbonate fillernor any efinite amount of-restoring agent used, the illustrative furnishes givenherein indr- .cate'that normally the carbonate filler con-'- stitutes a substantial percentage of thetotal furnish and consequently of the paper pro-' resent. It is thus apparent that my process;

in which a paper is produced containing a substantial quantity of carbonate 'filler, wholly unrelated to any pa rmaking pro cedure wherein alum or the 11 e is added to a paper mix for the purpose of substantially neutralizing the same so that the final paper will contain substantially no alkaline. constituents. v I -While I have described herein the use of rosin size as a size and alum. as a size precipitant ,toproduce asizing efiect, and have shown a method for the restoration of this sizing efiect'after it hassufiered deterioration ius or destruction, it is to be understood that sizes other than rosin size may be employed for sizing. 1 Such sizes are those which-have been derived by treatment with analkaline 'substance or the like from material originally of acid ch'aracteristics'or of a partially or completely. saponifiable nature, and which are used in conjunction with a size precipitant as alum. Exam les of such sizes are soaps, for instance'the oleates, and partially or wholly saponified waxes, for instance. saponified beesthe deterioration or destruction of the sizing as effect when such sizes are used is counteracted. It is to be understood, therefore, that the use of any such size and size precipitant to imart sizing to a paper in which my methodisused for the restoration of the sizing falls O0v within the scope of my invention.

Although there have been-proposals for sizing paper containing carbonate filler with the use of rosin (see, for example, Loshs British PatentNo. 2,664 of 1859, and CappazasBritish Patent No. 5,776 of 1899) the whole.

Wax. A size precipitant, other than alum,

method which I employ is wholly different from those disclosed in the above referred to patents as will be apparent or from any other method which has to my knowledge yet been proposed.

By the term carbonate filler as employed herein is meant the substantially water insoluble normal or basic carbonates of 'alka line earth metals (which expression is herein intended to include magnesium), or compounds, or double salts, or physically associated mixtures of these with one or more other acid soluble materials of a substantiala f ly water insoluble nature, these fillers whether simple or complex as above, bein characterized by the fact that, when agitate in contact with freshly boiled distilled'water in concentrated'suspension for say an hour, they impart to'the water a pH value which is on the alkaline side of the neutral point, and also by the fact that they give off carbon dioxide gas when brought into contact with an aqueous mineral acid,'e. g., hydrochloric acid.

Examples of such fillers are calcium carbonate, ofwhich lime mud from the cansticizing process is one form; calcium carbonate magnesium basic carbonate emplo ed in the paper disclosed in my U. S. Patent ha. 1,595,416 of August 10, 1926; and calcium carbonate magnesium hydroxide, disclosed in my U. S. Patent No. 1,415,391 of May 9,

.1922.- As will be apparent, these fillers are referred to not only in their chemically pure form but also in commercial formcontaim ing such impurities as may occur in such commercial products; and also when present with other material, so that they constitute only a part,-either major or minor, of the It should be stated that any given' filler of the type referred to is not necessarily of uniform particle size; nor are the average particle sizes of the fillers necessarily. a ike, as some of the fillers of the type -referred to have relatively coarse grain particles, whereas others are much more finely divided, and some are so finel divided that they may be said to approac or be in the colloidal condition.

Moreover, b x I mean to inc ude' pot only the case where the carbonate filler-ii is addedas such in the paper makin process, but also the-case where it may be a ded wholly or in part incorporated with fibrous 1material and/or other material such as paper coating constituents or the like. 'Such a case would be where apex: made with carbonate filler, either as a or coating constituent, or both, is reused in the aper making process. Such pa ers may be those known to the trade as old papers or old waste papers or waste papers in any form, or returned trimmings or damaged paper or the like, or they may be the broke, that is, the partially made, the imperfect, or the waste paper which accompanies the paper making, finishing, storing, packing, shipping, or the like operations in a paper mill, and which is reworked either in the same or some other mill. Such papers are sometimes reworked by themselves and added in broken down or in pulp form in the paper making process. being treated or cooked in some cases with or without chemicals and washed if desired, this reworking meaning to include thclprocess of deinking if such is practiced or of bleaching or of both deinking and bleaching, or sometimes they are added directly in the paper making process and broken down to pulp form therein. In any event they are a source of carbonate filler in the paper to he made. and are included in the term carbonate filler as used herein.

When I use the word paper herein, I use it in the broad sense to include products of manufacture of all types and of all weights and thicknesses, which contain as an essential constituent a considerable amount of prepared fibre and which are capable of being produced on a Fourdrinier, cylinder, or other forming, felting, shaping or molding machine.

Although the expression wet end of the paper machine may at times be used to convey various meanings, where I use the expression in the claims I intend it to include those instrumentalities provided in paper manufacture by which and /or in which the relatively concentrated mix is diluted, and treated, conveyedor fed up to the point of web formation, such as the mixing box, regulating and proportioning devices, riffiers, troughs, screens, machine head boxes, inlets, and the like, including also instrumentalitics used in the white water cycle. but I do not intend to include in this definition the Webforming device itself, that is, the moving wire in the case of a Fourdrinier machine or the cylinder mold in the case of a cylinder machine.

Although I have described in detail several illustrative furnishes I do not intend to be limited thereby, as my invention may be practiced with a broad variety of formulae, using various materials customa rily employed for various grades of paper in any suitable proportions. Moreover, various changes in procedure, ingredients, and arrangement of steps may be resorted to in the practice of my invention without departing from the spirit of my invention or the scope of the subjoined claims.

I claim:

1. The method of manufacturing a sized paper filled with carbonate filler comprising adding to a previously sized paper mix containing carbonate filler a sizing restoring material under conditions favoring the minimizing of the time of contact of the constituents of the mix, and thereafter making paper therefrom.

2. The method of manufacturing a sized paper filled with carbonate filler comprising adding to a previously sized paper mix containing carbonate filler a salt of a trivalent metal under conditions favoring the minimizing of the time of contact of the constituents of the mix, and thereafter making paper therefrom.

3. The method of manufacturing a sized paper filled with carbonate filler comprising adding to a previously sized paper mix containing carbonate filler a salt of aluminum under conditions favoring the minimizing of the time of contact of the constituents of the mix, and thereafter making paper therefrom.

4. The method of manufacturing a sized paper filled with carbonate filler comprising adding to a previouslv sized paper mix containing carbonate filler alum under conditions favoring the minimizing of the time of contact of the constituents of the mix, and thereafter making paper therefrom.

5. The method of manufacturing a sized paper filled with carbonate filler comprising adding to a previously sized paper mix containing carbonate filler alum under conditions favoring the minimizing of the intimacy and time of contact of the constituents of the paper mix, and thereafter making paper therefrom.

6. The step in a method of manufacturing a sized paper filled with carbonate filler comprising adding to a previously sized paper mix containing carbonate filler alum at a point in the process subsequent to that at which the paper mix exists in relatively concentrated form.

7. The step in a method of manufacturing a sized paper filled with carbonate filler comprising adding to a previously sized paper mix containing carbonate filler alum at a point in the process where the concentration of the solids is not over one and one half per cent. on the dry basis.

8. The step in a method of manufacturing a sized paper filled with carbonate filler comprising adding to a previously sized paper mix containing carbonate filler alum at a point in the paper making process not more than five minutes prior to web formation.

9. The step in a method of manufacturing a sized paper filled with carbonate filler comprising adding to a previously sized paper mix containing carbonate filler alum at the wet end of the paper machine.

10. That step in a method of manufacturing a sized paper filled with carbonate filler comprising adding on aluminum salt at the wet end of a paper machine to a paper mix containing fibrous material, carbonate filler, and. a potential sizing agent.

11. That step in a method of manufacturing a sized paper filled with carbonate filler comprising adding alum at the wet end of a paper machine to a paper mix containing fibrous material, carbonate filler, and a potential sizing agent.

12. The steps in a method of manufacturing asized paper filled with carbonate fillercomprising mixing fibre, size, size preclpitant, and carbonate filler, and adding to such mix a sizing restoring material at the ,wet end of the paper machine.

13. The steps in amethod of manufacturing a sized paper filled with carbonate filler comprising mixing fibre, size, alum, and carbonate filler, and adding a subsequent quantity of alum at the wet end of the paper machine.

14. The steps in a method of manufacturing a sized paper filled with carbonate filler comprising mixing fibre, rosin size, alum, and carbonate filler, and adding a subsequent quantity of alum at the wet end of the paper machine.

15. The steps in a method of manufacturing a sized paper filled with carbonate filler comprising mixingfibre, rosin size, alum, and carbonate filler in the beater, and addin a subsequent quantity of alum at the wet end of the paper machine.

16; The steps in a method of manufacturing a sized paper filled with carbonate filler comprising precipitatl 3g a size with alum in the heater, and adding a subsequent quantity of alum at the wet end of the paper machine.

17. That step in a process of sizing paper containing carbonate filler comprising the restoration of sizing in a paper mix by theaddition of a sizing restoring material at the wet end. of the paper machine.

18. That step in the process of sizing paper containing carbonate filler comprising the restoration of sizing by addition of alum atthe wet end of the pa er machine.

19. The method 0 restoring the sizing to a previously sized paper mix containing carbonate filler whose sizing has been deteriorated by the carbonate filler, comprising the addition of alum to said mix at the wet end of the paper machine.

20. The steps in a method of manufacturing a sized paper filled with carbonate filler comprising an alkaline earth. metal carbonate consisting of mixing fibre, size, alum, and an alkaline earth metal carbonate, and adding a subsequent quantity of alum at the wet end of the paper machine.

21. The steps in amethod of manufacturing a sized paper filled with carbonate filler comprising calcium carbonate consisting of mixing fibre, size, alum, and calcium carbonate, and adding a subsequent quantity of alum at the wet end of the paper machine.

22. The steps in a method of manufacturing a sized paper filled with carbonate filler comprising calcium carbonate and magnesium compound consisting of mixing fibre, size, alum, and calcium carbonate and magnesium compound, and adding a subsequent quantity of alum at the wet end of the paper machine.

23. The method of manufacturing a sized paper filled with carbonate filler comprising calcium carbonate magnesium hydroxide consisting of mixing fibre, size, alum, and calcium carbonate magnesium hydroxide, adding a subsequent quantity of alum at the wet end of the paper machine, and making paper from the resulting mlx.

24:. The method of manufacturing a sized paper filled with carbonate filler comprising adding to a previously sized paper mix containing carbonate filler a sizing restorin material under conditions favoring the minlmiz ing 01' the intimacy and time of contact of the constituents of the mix, and thereafter making paper therefrom.

In testimony whereof I affix my signature.

HAROLD ROBERT RAFTON. 

